Electric discharge apparatus



Nov. 26, 1935. J. w. DAWSON ELECTRIC DISCHARGE APPARATUS Filed June 29, 1933 4 Sheets-Sheet 1 INVENTOR John W. Dawson.

BYO/ I ATTOR Y Nov. 26, 1935. J. w. DAWSON ELECTRIC DISCHARGE APPARATUS Filed June 29; 1953 4 Sheets-Sheet 2 Fig. 3.

Fig. 4,

INVENTOR John W. Dawson.

WITNESSES:

ATTORN Nov. 26, 1935. w DAWSON 2,021,888

I ELECTRIC DISCHARGE APPARATUS Filed June 29, 1933 4 Sheets-Sheet 3 Fiy. 5.

Fly. 8.

WITNESSES: INVENTOR John W. Dawson.

Jim J W I BY ATTORNEY Patented Nov. 26, 1935 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE APPARATUS Pennsylvania Application June 29, 1933, Serial No. 673,237

23 Claims.

My invention relates to electric discharge apparatus and it has particular relation to apparatus of the type utilized in power supply systems.

The present application is a continuation in part of my application Ser. No. 653,451 filed Jan. 25, 1933, and assigned to the Westinghouse Electric & Manufacturing Company. In its more restricted scope, the present application is, moreover, an improvement of the system shown and described in my Patent No. 1,928,812, filed December 19, 1930, granted October 3, 1933, and assigned to the W. E. & M. Co., reissue applied for January 11, 1934, Serial No. 706,303. For this reason the objects accomplished by my present invention can perhaps be most adequately explained with reference to the patent.

In my aforesaid Patent No. 1,928,812, a power supply system for vibratory apparatus, such as a mechanical shaker screen, for example, is shown and described. The element that is to be vibrated is coupled to an electromagnet that is intermittently energized and deenergized. When the magnet is so energized and deenergized, it sets the vibrating element in vibration. The electromagnet is energized from a suitable power source through a plurality of electric discharge devices of the asymmetric type.

The power source is of the alternating current type and, in practice, has the usual commercial frequency of cycles per second. The frequency at which it is desired to motivate the vibrating element is, in general, of the order of 10 or 15 cycles per second, and the electric discharge devices are utilized for the purpose of controlling the supply of intermitting current to the magnet.

The electric discharge devices of the type preferably utilized in the system described in the above-mentioned applications each have an anode, a cathode and a control electrode, all immersed in a gaseous medium at a low pressure. Each of the devices has only an energized condition and a deenergized condition and is capable only of abrupt transition from one condition to the other. The particular condition of the device at any given time depends on the potential applied between the anode and the cathode (which will be herein designated as the principal potential) and on the potential impressed between the control electrode and the cathode (which will be herein designated as the control potential). When the principal potential is positive 1. e., the anode is positive relative to the cathode) and of proper magnitude and when the control potential is of proper magnitude relative to the principal potential, the electric discharge device is energized. It thereafter remains in its energized condition regardless of the variations in magnitude of the control potential until the principal potential is reduced to a value substantially below the ionization potential of the gas in which the electrodes are immersed.

When the principal potential impressed on the electric discharge device is an alternating po- 10 tential, the device remains deenergized as long as the control potential remains below a predetermined value, (which I shall herein designate as the limiting control potential). If the corn trol potential at any time during the interval 15 during which the principal potential is positive rises above the limiting control potential, the electric discharge device becomes energized and remains energized during the remaining portion of the positive half cycle of principal potential 20 and it becomes deenergized only when the prin cipal potential is sufiiciently reduced.

In the system described in my aforesaid pa ent, the electric discharge devices are supplied with commercial alternating potential. They are, therefore, even when once energized, deenergized with a periodicity dependent on the frequency of the source and with this periodicity are subject to the control of the control potential. The control potential is varied in a manner corresponding to the frequency at which it is desired to energize the vibrating element of the shaker.

When the control potential impressed on the electric discharge devices is of proper magnitude the devices are alternately energized, as positive principal potential impressed on their electrodes, and the load is supplied with current. Subsequently, the control potential impressed on the electric discharge devices is so varied that {10 they are both deenergized, in which case, the electromagnet of the vibrator system should also be deenergized. However, it will be noted that during the energizing period a magnetic flux of considerable magnitude is built up in the electromagnet. As the flux collapses a back potential appears across the terminals of the electromagnet, and this potential would tend, in the absence of proper: suppressing apparatus, to mainy tain the last of the electric discharge devices to be energized in spite of the fact that the control potential. and the principal potential supplied by the power source is at a value corresponding to a deenergized condition. Essentially what happens in such a case is that the back potential of 55 the load is greater than the forward potential of the source and in consequence thereof the principal potential impressed on the electric discharge device remains positive.

To suppress this condition, I have, in accordance with the above-mentioned application, provided a dissipating-network which is asymmetrically conductive. The network is connected across the windings of the electromagnet in such manner that it is non-conductive to the current flowing into the vindings or" the electromagnet when the latter is being energized, but is conductive to a current transmitted under the backelectrcmotive force generated by the collapse of the flux in the electrornagnet. lhe energy stored in the electromagnet is thus dissipate-d in the network and prevents the electric discharge devices from remaining ehergized when they should be deenergized.

It is to be noted that the use of the dissipating network in the system described in my earlier application results in the loss of a considerable portion of the energy supplied to the load. The operation of systems in which the currents transmitted through the load are comparatively high therefore, involves considerable expense. In addition I have found that suppressing networks of the type utilized in the systems described in my earlier application do not always operate en ciently to suppress the ha i: electro-motive force and do not suppress this electri -motive force at the high rate that is necessary for proper operation.

It is, accordingly, an object of my invention to provide a mechanism for intermittently sup plying power to a load of the type having the property of storing a portion of the energy supplied thereto, without suffering a large incidental power loss from the necessary intermittent dissipation of the energy stored in the load.

Another object of my invention is to provide apparatus incorporating electric discharge devices for supplying power intermittently to a load or" the type having the property of storing a portion of the energy supplied thereto, without entailing the loss of the energy stored in the load.

Still another object of my invention is to provide apparatus incorporating electric discharge devices for supplying a load of the type having the property of storing a portion of the energy supplied thereto, wherein the energy stored in the load shall be dissipa ed at at least as high a rate as the rate at which it is stored.

A further object of my invention is to provide highly eiiicient apparatus of the type 'icorporating electric discharge devices for intermittently supplying power to a load of the type having the property of storing a portion of the energy supplied thereto.

A still further object of my invention is to provide highly emcient apparatus for converting power pulsating at a given frequency into power pulsating at a predetermined different frequency.

A more specific object of my invention is to provide an efficient power supply system of the type incorporating electric discharge devices for intermittently supplying current to a load of the inductive type.

Another specific object of my invention is to provide an eihcient power supply system without moving mechanical parts for supplying power at a predetermined periodicity to a load of the type having the property of storing a portion of the energy supplied thereto.

An incidental object of my invention is to provide, in a power supply system incorporating an electric discharge device of the type having a starting electrode through which a current is transmitted to initiate a discharge between the principal electrodes, a starting circuit in which the energy consumed shall be a minimum.

Another incidental object of my invention is to provide, in a power supply system of the type incorporating an electric discharge device having a plurality of principal electrodes and a starting electrode through which starting current shall intermittently be transmitted to a cooperating principal electrode, to intermittently initiate the discharge between the principal electrodes, a starting circuit in which the starting current shall be so decreased before its interruption that the objectionable phenomena inherent in the interruption of comparatively large currents shall be suppressed.

More concisely stated, it is an object of my invention to provide a power supply system of the type incorporating electric discharge devices either with starting electrodes or control electrodes that shall operate with high efhciency and that shall be comparatively inexpensive to maintain.

According to my invention, I provide a power supply system of the type incorporating electric discharge devices in which the control potential of the electric discharge devices is so varied that energy is supplied to the load for a predetermined interval of time, and a portion of the energy is stored in the load. After this interval of time the relationship of the load and the power source is so varied that the energy stored in the load is fed back into the power source through the electric discharge devices when the potential of the power source is of opposite polarity to the potential under which the load was energized. This procedure is repeated periodically and the load is thus periodically energized and deenergized without loss of the energy stored in the load.

In accordance with one embodiment of my invention, the control potential for the electric discharge devices is varied by a system incorporating a plurality of. current interrupting contacts that are properly motivated. In accordance with another emhodiment of my invention, the condition of the electric discharge devices is controlled by s fting the phase of the control potential at the desired periodicity. According to one modification of this embodiment of my invention, the phase shift is attained by the rotation of a suitable movable contactor or commutator in and out of engagement with cooperating fixed contact elements, and in accordance with another modification of embodiment, the phase shift is attained by utilizing a suitable non-mechanical timing circuit.

As will be explained hereinafter, my invention is applicable both to power supply systems incorporating electric discharge devices of the type having control electrodes, and to power supply systems of the type incorporating electric discharge devices having starting or ignition elec trodes, such as the Ignitron tube, for examp e. The latter discharge devices will be explained more in detail hereinafter in connection with Figs. 3 and 4.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments, when read in connection with the accompanying drawings; in which Figure 1 is a diagrammatic view showing an embodiment of my invention utilizing hot-cathode electric discharge devices;

Fig. 2 is a plot illustrating the operation of the system shown in Fig. 1;

Fig. 3 is a diagrammatic view showing a modification of my invention in which the electric discharge devices are of the type incorporating starting or make-alive electrodes;

Fig. 4 is a diagrammatic view showing a modification of the system in which the electric discharge devices are of the type incorporating starting or make-alive electrodes;

Fig. 5 is a diagrammatic view showing a modi fication of my invention in which the desired result is attained by phase shift of the control potential or of. the starting current;

Fig. 6 is a vector diagram illustrating one feature of the operation of the system shown in Fig.

Fig. 7 is a graph corresponding to Fig. 6;

Fig. 8 is a vector diagram illustrating another feature of the operation of the system shown in Fig. 5;

Fig. 9 is a graph corresponding to Fig. 8;

Fig. 10 is a diagrammatic view showing a further modification of my invention in which moving mechanical parts are not utilized;

Fig. 11 is a vector diagram illustrating a feature of the operation of the system shown in Fig. 10; and

Fig. 12 is a graph illustrating the operation of the system shown in Fig. 10.

The apparatus shown. in Fig. 1. comprises a plurality of power supply bus lines I which are supplied with alternating current from a power source (not shown) and to which the terminals of the primary 3 of a transformer 5 are connected. The secondary l of the transformer 5 provided with a section 9 equipped with a plurality of terminal taps ll and i3 and an intermediate tap 55. The terminal taps H and I3 of the section 9 of the secondary l are connecteddirectly to the anodes H and I8 of plurality of electric discharge devices 2! and 23. The cathodes 25 and 21 of the electric discharge devices 2| and2i5 are of the so-called hot-cathode type, as shown, and are connected to each other at a junction point 25. The intermediate i 5 of the secondary section 5 is connected to the junction point 29 of the cathodes through. an inductive, power-consuming load 3! that is to be supplied with po er from the source I through eleo tric discharge devices 2! and 23.

The electric discharge devices 2| and 23 are preferably of the grid-glow type utilized in the system described in aforesaid Patent No. 1,928,812. I have found that for many purposes the Westinghouse grid-glow tube KU 628 is of considerable utility in the present connection. However, if the requirements of the load circuit permit a smaller tube, the Westinghouse gridglow tubes KU-627 or KU-610, for example, may be utilized.

In the customary practice of my invention the principal potential has a peak value that is or the order of 100 volts and for the particular electric discharge devices that are preferably utilized, the corresponding limiting control potential is of the order of volts. When the control potential is raised to a value above (or more positive than) this limiting value during the interval during which positive principal potential is supplied, the electric discharge device 2| or 23 for which this condition occurs is energized and remains energized during the remainder of the positive half cycle of principal potential. 5 The condition of the electric discharge devices 2! and 23 in the system shown in Fig. l is controlled from .a plurality of rotating contactors or commutators 33 and 35 that are rotated by a synchronous motor 31 energized from the bus 10 lines I of the power supply source and, therefore, energized in synchronism with the source. Each of the commutators 33 and 35 is, respectively, equipped with an inner conducting ring 39 and 4| and with an outer conducting ring 43 and 45 provided with a plurality of specially positioned insulating inserts 41 and 49 and 5|, 53, and 55. A plurality of brushes 51 and 59, connected to the negative terminal of an auxiliary power source (ii that may be preferably a battery of voltaic 201 cells, engage the inner rings 39 and 4|; while a plurality of brushes 63 and 55, connected to the control electrodes 5'! and 69 of the electric discharge devices 2! and 23, respectively, through suitable grid resistors H and I3, engage the outer rings 43 and 45. The positive terminal of the battery 6| is connected to the junction point 29 of the cathodes 25 and 21.

When the brushes 63 and 65, engaging the outer rings 43 and 45, are in contact with the 0 conducting portions of the rings, the negative terminal of the battery 6!, to which the inner brushes 5'. and 59 are connected, is connected through the rings and brushes to the control elec trodes ii! and 69 of the electric discharge devices I 2! and 23. This potential is of such magnitude that the control potential is more negative than the limiting control potential for the electric discharge devices. and the electric discharge devices remain in their deenergized condition. On the 40 other hand, when either of the outer brushes B3 or 65 is engaged by an insulating insert 41 or .9 or 5!, 53 or 55, the corresponding control electrode 61 or 69 is disconnected from the auxiliary power source 6!, and its potential is raised sub- 45 stantially to the potential of the corresponding anode H or H) to which it is connected through another resistor 15 or 11 of suitable character. When the control electrode ill or 59 of either electric discharge device 2| or 23 is thus raised to the 50 anode potential, at a time when the anode potential is positive. the electric discharge device becomes energized and transmits current through the load 3 I.

The insulating segments 41 and 49, and Si, 53 55 and 55 and the outer brushes 53 and 55 are so disposed relative to each other that the following series of conditions exist in the electric discharge devices ZI and 23:

(l) The electric discharge devices 2! and 23 arealternately energized by interrupting their normally existent negative control potential connections, substantially at the beginnings of each of a plurality of successive half-cycles of positive potential, until a full current of predetermined magnitude is built up in the load 3|, as will be explained in connection with Fig. 2.

(2) This full-current condition is necessarily attained during a half-cycle in which positive principal potential is supplied to one of the elec- 70 trio discharge devices (e. g. the device 2!) and negative principal potential is supplied to the other discharge device (e. g. the device 23). At the beginning of the next half-cycle of principal potential, when the principal potential supplied to the last-mentioned discharge device 23 becomes positive and the principal potential supplied to the former discharge device 2| becomes negative, the control potential supplied to the discharge device 23 by the battery BI is not interrupted, as heretofore at the beginnings of each half-cycle of the supply-voltage, but remains negative, and hence the discharge device 23 does not become energized.

(3) By reason of the non-energization of the electric discharge device 23, the discharge is not transferred from the formerly energized electric discharge device 2|, and the latter, in spite of the fact that its principal potential is now nega tive, remains in its energized condition and draws current from the load, returning power to the power-supply line, during nearly all of one half-cycle.

(4) Nearly, but not quite, at the end of the last-mentioned half-cycle of principal potential, the second discharge device 23 (which now has positive principal potential impressed thereon) is energized by the engagement of its corresponding outer brush 65 with an insulating segment such as 49, resulting in the removal of the negative potential from its control electrode 69.

(5) The latter electric discharge device 23, therefore, becomes energized and shunts out the former electric discharge device 2|, extinguishing the device 2|, and for the remainder of its positive half-cycle of principal potential, the device 23 feeds current into the load 3|.

(6) However, since the principal potential on the discharge device 23, as supplied by the secondary of the transformer, soon becomes negative, this discharge device 23 also begins to draw current from the load and thus further decreases the current passing through the load, until nearly at the end of its half-cycle of negative principal potential, when the former device 2| is again energized and repeats the performance just described for the device 23.

(7) This procedure is repeated until the current in the load is substantially zero.

(8) At this juncture, or at a predetermined interval later, one of the electric discharge devices 2| is again energized substantially at the beginning of its positive half cycle of principal potential and the load 3| is again supplied with current from the power source.

It is to be noted that in accordance with the above enumerated steps the load 3| is first supplied with power under the positive electromotive force of the power source and subsequently it gives up its stored energy when the electromotive force of the power source is negative. Since, in an ordinary power supply system the positive half wave of output potential is equal in magnitude to the negative half wave of output potential, the load 3| may be deenergized at a rate which is at least as high as the rate at which it is energized. That is to say, since the force supplying power to the load is of the same magnitude as the force withdrawing useful power from the load, to say nothing of the work being done by or in the load, the demagnetizing operation may take place at as great a rate as the magnetizing operation, or even at a greater rate and the difficulty which arises in the systems constructed in accordance with my earlier application does not exist.

It is seen that, in accordance with the above procedure, the load 3| is supplied intermittently with power and intermittently feeds back power to the power source. In this manner the exciting coil of a vibrating system such as a shaker screen, may be intermittently energized at a high efliciency.

The proper spacing of the insulating segments on the outer rings 43 and 45 is shown in detail in Fig. 1. The rings 43 and 45 are rotated in a counter-clockwise direction. The cycle of operations may be regarded as beginning with the engagement of the upper insulating segment 5| of the left hand ring 45 with the brush 65 connected to the control electrode 69 of the righthand electric discharge device 23. The engagement of the two contact elements 5| and 65 takes place at the beginning of the positive half cycle of principal potential applied to the right hand electric discharge device 23. Current is thereupon supplied through the electric discharge device 23 to the load 3|.

The next element to be engaged by a brush is the lower insulating insert 47 of the right-hand outer ring 43 which is engaged by the brush 63 connected to the control electrode 61 of the left hand electric discharge device 2|. The former insulating insert 5| and the latter insulating segment 41 are so spaced with reference to each other and to the corresponding brushes 65 and 63 that the engagement of the brush 63 with the insert 41 takes place at the beginning of the half cycle of positive principal potential applied to the left-hand electric discharge device 2| and consequently at the beginning of the negative half cycle of principal potential applied to the right hand electric discharge device 23. The left-hand electric discharge device 2| is, therefore, energized while the right-hand electric discharge device 23 is deenergized, and the supply of current to the load 3| is continued.

At the beginning of the next successive half cycle of potential the brush 65 that is connected to the control electrode 69 of the right-hand electric discharge device 23 is engaged by the insulating insert 53 of the left-hand outer ring 45. The right-hand electric discharge device 23 is, therefore, reenergized while the left hand device 2| is deenergized, and the current which is transmitted to the load 3| is further increased.

At the beginning of the next subsequent halt cycle of principal potential, neither of the brushes 63 or 65 is engaged by an insulating segment, and the inductive load 3| now supplies energy to the power source through the electric discharge device 23 that was last energized. This condition continues until nearly the end of that half cycle of principal potential. At this point, the remaining insulating segment 49 of the righthand outer ring 43 is engaged by the brush 63 which is connected to the control electrode 61 of the left-hand electric discharge device 2|, and the latter device is energized. When it is so energized, the left hand device 2| shunts out the other electric discharge device 23 and the latter device is deenergized. The left hand electric discharge device 2| now continues in its energized condition during the remainder of the half cycle in which it has been energized, and during the subsequent half cycle in spite of the fact that the principal potential supplied by the power source takes on a negative polarity during the latter half cycle. The load 3| supplies power through the device 2| to the power source during the latter half cycle of principal potential. When the end of this half cycle is approached, the brush 65 which is connected to the control electrode 69 of the right-hand electric discharge device 23 is connected to the remaining insulating principal potential.

segment 55 of the left-hand outer ring, and this electric discharge device is energized, nearly at the end of its positive half cycle of principal potential, and shunts out the other electric discharge device 2|. It supplies current to the load for the short interval remaining of the positive half cycle of principal potential applied to it and then draws current from the load 3|. At this point the current in the load 3| is reduced substantially to zero and the above-described series of steps isrepeated.

The operation of the system is illustrated in detail in Fig. 2. The principal potential applied to the right-hand electric discharge device 23 is :shown as a full-line sine curve 79 having a plurality of positive half waves 8|, 83 and 85, plotted against time. The positive half waves of principal potential applied to the left-hand electric discharge device 2| are shown as broken-line halfwave sine curves 81, 89, and 9|. plied to the load 3| is shown as a full line curve 93 that extends above the curves representing the principal potentials supplied to the electric discharge devices 2| and 23. The outer rings 43 and 45 of the commutators 33 and 35 are plotted developed, and in the plot the insulating inserts 47, 49, 5|, 53, and 55 are shown, with reference to the half waves of principal potential, at the points at which they are engaged by the brushes .63 and 65.

- It is to be noted in Fig. 2 that the firstupper insulating segment 5| of the left-hand outer contactor ring 45 is shown in a position corresponding to the beginning of the positive half cycle of At the starting point represented in Fig. 2, the insulating segment 5| is engaged by the brush 65 in Fig. 1. The electric discharge device 23 to which the positive principal potential is applied at this-point becomes energized and supplies current to the load 3|, gradually building up in opposition to the inductance of the load. The current supplied through the electric discharge device 23 is represented in Fig. 2 by the shaded area 95 under the load current curve 93. The insulating insert 41 of the right-hand contact ring 53 in Fig. 1 subsequently engages its corresponding brush 63 at the beginning of the positive half wave 81. of principal potential which is supplied to the other electric discharge device 2| as shown in Fig. 2. At this point, the electric discharge device 2| is energized and current is supplied to the load through it, building up still further, as shown in Fig. 2. At the next half wave of principal potential, an insulating'insert 53 on the left hand contactor ring 45 is engaged, and current is supplied to the load 3| as represented by the shaded area 91 under the current curve 93. i

At the beginning of the next half Wave 89 of principal potential, neither of the electric discharge devices 2I or 23 is energized by variation or interruption of the control potential, which is normally strongly negative, by reason of theconnection of the battery 6|. However, the righthand electric discharge device 23, which was energized the beginning of the half cycle 83, remains in its energized condition and continues to draw current from the load, deriving its principal voltage from the collapsing magnetic lines of force in the inductive impedance of the load. This condition is represented by the shaded area 99 under the current curve 93. By reason of the fact that the load 3| supplies energy to the power source, besides consuming energy within itself, the current passing through the load is The current sup-- decreased and it is so shown in Fig. 2. Near the end of the half cycle 89 of positive principal patential applied to the left-hand electric discharge device 2|, the brush 63 on the right-hand outer ring 43 in Fig. 1 is engaged by the insulating insert 49. The left-hand. electric discharge device 2| is, therefore, energized and for a short interval of itme current is supplied through it to the load 3|. This condition results in an increase in the current transmitted through the load, as is illustrated by the rise of the current curve 93 in the region following the point at which the left-hand electric discharge device is energized. However, the principal potential applied. to the now energized electric discharge device 2| from the source soon becomes negative and energy is supplied to the power source by the load 3|. The current in the load is, therefore, further decreased.

Finally, the right-hand electric discharge device 23 in Fig. 1 is energized substantially at the end of its positive half cycle 85 of positive principal potential, and for a short interval of time the current in the load increases, as shown by the rise in the current curve 93 in Fig. 2. However, the principal potential applied to the righthand electric discharge device 23 from the source soon becomes negative and the current passing through the load falls to substantially zero value as shown in the shaded area under the cur rent curve 93. After this condition occurs the right-hand electric discharge device 23 is again energized substantially at the beginning of its positive half cycle and the above-described series of steps is repeated.

It is to be noted that the synchronous motor 31 in the system shown in Fig. 1 is of the type incorporating an externally-excited field. When a motor of this type is synchronized with a power source the angular position of any point on the rotor bears a fixed relationship to the half waves of alternating potential that are supplied to the armature. Consequently, if the commutators 33 and 35 are properly positioned on the rotor shaft, the system will always start and operate with the brushes 63 and 65 engaging the inserts 41,. 49, 53, and 55 at instants corresponding to the points at which it is desired that the brushes should engage the inserts for proper operation.

- In Fig. 3 my invention is shown as applied to: a system incorporating electric discharge devices .13 and H of the make-aiive type, such as the Ignitron tube. An electric discharge device ofv this type comprises, in general, a vaporizable reconstructing cathode of a material such as mercury or tin, and an anode to cooperate with the cathode. A poorly conducting make-alive electrode composed of carborundum, boron carbide, silicon carbide, boron, silicon, a glow bar rod, Nernst filament material, ferro-silicon, galena or a number of other similar materials, is immersed in the mercury or tin, and when a so-called starting current of a predetermined magnitude is caused to flow from the starting electrode to the cathode, a discharge is initiated between the principal electrodes. By a poorly conducting makealive electrode I means an electrode having a resistivity of not greater than 10 ohms per centimeter cube.

In the system shown in Fig. 3, the make-alive electric discharge devices I03 and M5 are connected to the secondary of the transformer 5 in the same manner as the corresponding electric discharge devices 2| and 23 are connected in the system shown in Fig. l. The anodes I01 and I09 of the electric discharge devices I03 and I05 are, respectively, connected to the terminal taps II and I3 of the secondary 1, while the cathodes H I and I I3 of the electric discharge devices are connected to each other .and their common junction point 29 is connected to the intermediate tap I5 of the secondary through the load 3 I.

A plurality of commutators H5 and I I1 are associated with the make-alive electrodes H9 and I2I of the electric discharge devices I03 and I05. The commutators H5 and H1 might be, so to speak, regarded as the electrical negatives of the commutators 33 and 35 associated with the control electrodes 61 and 69 of the electric discharge devices 2| and 23 of the system shown in Fig. 1. The inner elements in the commutators are conducting rings 39 and H as in the former system. However, the outer elements comprise insulating rings I23 and I 25 in which are inserted a plurality of conducting inserts I21 and I29 and I3I, I33 and I35 which are connected to the inner rings 39 and M, respectively. The conducting inserts I21, I29, I3I, I33, and I35 are located at points in the rings I 23 and I25 that correspond to the positions of the insulating inserts 41, 49, 5|, 53, and 55 in the outer rings 43 and 45 of the system shown in Fig. 1. The conducting inserts I21 and I29 are conductively connected to the corresponding inner ring 39 while the conducting inserts I 3 I, I33 and I35 are connected to the corresponding inner ring 4I.

The brushes 51 and 59 that are in engagement with the inner conducting rings 39 and H are connected to the respective anodes I01 and I09 of the electric discharge devices I03 and I05, while the brushes 63 and 65 that are in engagement with the outer rings I23 and I25 are connected to the make-alive electrodes H9 and I of the respective electric discharge devices through suitable current limiting resistors I31 and I39. When a brush 63 or 65, connected to a make-alive electrode H9 or I2I, engages a conducting insert I21 or I29, or I3I, I33, or I35, the make-alive electrode is connected to one of the terminals of the power source and current is transmitted through the electrode and through the corresponding cathode III or II3. If the current is of proper magnitude and polarity, the corresponding electric discharge device I03 or I05 is energized or caused to become conducting.

For the present purpose let it be assumed that, at the instant corresponding to the position of the elements as shown in Fig. 3, the right-hand terminal I3 of the secondary I of the transformer 5 is positive relative to the intermediate tap I5 and the left-hand terminal I I is negative relative to the intermediate tap. At this instant the brush 65 connected to the make-alive electrode I2I of the right-hand electric discharge device I05 is engaged by the conducting segment I3I and current is transmitted through the make-alive electrode in a proper direction for ignition. The righthand electric discharge device I05 having at this time the proper principal potential applied thereto is, therefore, energized when the make-alive current attains the starting value, and current is supplied to the load 3|.

Since the circuit shown in Fig. 3 involves a feature of considerable importance, it may be well to digress here to explain this feature. It is to be noted that each of the make-alive circuits is connected .at one of its terminals to the anode I01 or I09 of its associated electric discharge device I03 or I05. and at the other terminal it is connected to the cathode III or II 3 of the associated electric discharge device. Consequently, when one of the electric discharge devices, I05 for example, is energized, the corresponding makealive network is shunted out, and the current which was originally transmitted from the then positive terminal I3 of the secondary I, through the contact elements 59, 4I, I3I, and 65 thence through the make-alive electrode I2 I of the righthand electric diwharge device I05, the cathode II3 of this device and the load 3I, to the intermediate tap I5 of the secondary, is now transmitted betweenthe principal electrodes I09 and H3 of the right-hand electric discharge device I05, and thence through the load 3| to the intermediate terminal I5 of the secondary. The current supplied to the make-alive electrode I2I is, therefore, necessarily decreased after the electric discharge device is energized, and hence the current that must be interrupted at the contactor III by the disengagement of the conducting insert I3I from the brush 55 which is connected to the make-alive electrode I2I, is comparatively small. In this manner, sparking between the contacts and the brushes, which would deleteriously affect these elements, is suppressed, and the magnitude of the make-alive current drawn by the high resistance starting circuit is maintained at a minimum. It is to be noted that the latter advantage is of considerable importance since, in make-alive electric discharge devices of this type, the starting current may have a magnitude as great as 5 or 10 amperes. By utilizing the system shown in Fig. 3 with the feature described hereinabove, not only are the contact members of the commutators II 5 and H1 protected from disintegration, but the starting electrodes are prevented from becoming excessively heated, and considerable power is saved.

To revert now to the essential features of the system shown in Fig. 3, the current transmitted between the principal electrodes I09 and H3 of the right-hand electric discharge device I05, when once initiated, continues during the remainder of the positive half cycle of principal potential impressed on this device. Since the potential drop between the anode I09 and the cathode II3 of the electric discharge device I05 is comparatively small when the device is energized, the cathode H3 is, during this interval, at substantially the potential of the anode I09 and consequently at the potential of the righthand terminus I3 of the secondary 1.

At the beginning of the subsequent half cycle of principal potential, a conducting insert I21 in the right-hand ring I23 is engaged with the brush 63 which is connected to the left-hand starting electrode H9. The difference of potential between the starting electrode H9 and its corresponding cathode I II is now substantially equivalent to the potential difference between the two terminal taps II and I3 of the secondary 1 of the transformer 5. When the circuit through the starting electrode H9 is completed by the engagement of the conducting insert I21 and the brush 63 connected to the starting electrode, sufiicient ;current is transmitted through the starting electrode to energize the left-hand electric discharge device I03, and when it is energized, current is transmitted through it and to the load 3I.

The above series of steps are repeated until suitable current is built up in the load 3I. After this condition is attained, the inserts I29 and '-tric discharge device I03 or I05.

I 35, being properly positioned in the rings I23 and I25, engage the brushes 63 and 65 at instants corresponding to the latter portions of the positive half cycles of principal potential as previcusly explained, and the electric discharge devices |03 and I05 are so energized as to draw current from the load 3| and supply it to the power source in the manner explained with regard to the system shown in Fig. 1.

The system shown in Fig. 4 is largely similar to the system shown in Fig. 3. Experiments with make-alive electric discharge devices have demonstrated that their operation is most satisfactory when current is transmitted through the starting electrode only in a direction proper to ig nition, and is not transmitted in the opposite direction. For this reason, the preferred practice has been to energize the make-alive circuit of an electric discharge device through an asymmetric electric discharge device preferably of the hot cathode grid-glow type.

A system in which this procedure is followed is shown in Fig. 4. In this system, the makealive electric discharge devices I03 and I05 are connected to the secondary I of the transformer 5 and to the load 3! in the same manner as the corresponding devices are connected in the sys tern shown in Fig. 3. However, a plurality of hot-cathode electric discharge devices I49 and I5I are provided, having principal electrodes I4I, I43 and I45, I41 which are connected in series with the respective make-alive electrodes H9 and I2I, the corresponding cathodes III and N3 of the electric discharge devices I03 and I05, and the corresponding terminals II and I3 of the secondary I. The hot-cathode electric discharge devices I49 and I5I have control electrodes I53 and I which are supplied with potential from a system of commutators 33 and 35 and a battery 6| that are identical in structure and arrangement to the corresponding elements of the system shown in Fig. 1. The hot-cathode electric discharge devices I49 and I5! are energized in the same sequence as the devices 2| and 23 of the system shown in Fig. 1, and provide for the excitation of the make-alive electric discharge devices I03 and I95 in the proper sequence to feed the load 3| and to draw current from the load, as has been explained hereinabove.

When a hot-cathode electric discharge device I49 or I5I is energized, current is transmitted through it and through the make-alive electrode 9 or I2I of the corresponding make-alive elec- The makealive electric discharge device is, therefore, energized and supplies power to the load 3| or draws current therefrom in the manner already outlined.

It is to be noted that the anodes I 4| and I45 of the hot-cathode electric discharge devices I49 and I5I are each connected to an anode I01 or I09 of the corresponding make-alive electric discharge device I 03 or I05, while the principal circuits of the make-alive electric discharge devices are connected in shunt with the corresponding make-alive circuits including the hot-cathode electric discharge devices. When a make-alive electric discharge device is energized therefore, the corresponding hot-cathode electric discharge device and its cooperative circuit is shunted out and deenergized. This feature of the system is similar to the feature discussed hereinabove and is important since, by utilizing it, a saving of considerable power may be effected.

It may aid to an understanding of the operation, to follow the circuits of the system shown in Fig. 4 in detail for one cycle of operation of the system. The hot-cathode electric discharge devices I49 and I 5| are energized at the beginning or near the end of a half cycle of positive principal, potential depending on the relative disposition of the brushes 63 and 65, and the insulating inserts 41, 49, 5|, 53, and 55. Assume, for example, that the right-hand hot-cathode electric discharge device I5I is energized. Current is transmitted through a starting circuit extending from the right-hand terminal I3 of the secondary I of the transformer 5, through the principal circuit of the hot-cathode electric discharge device I 5|, the make-alive electrode I2I of the right-hand electric discharge device I05, the cathode I I3 of this discharge device, and the load 3|, and thence to the intermediate terminal I5 of the secondary of the transformer. When the current transmitted through the make-alive electrode I2I attains the proper magnitude, the righthand electric discharge device I05 is energized, and current is transmitted between the principal electrodes I09 and N3 of the device and through the load 3|. The potential difference between the anode I09 and the cathode II3 of the righthand electric discharge device I05 and, therefore, the potential difference between the anode I45 and the cathode I4I of the corresponding hot cathode electric discharge device I5I is reduced to a small value and the latter device is deenergized. The same series of steps is repeated for the system on the left-hand side, and current is supplied to the load 3| from the power source and from the load to the power source in the manner explained hereinabove.

While hot cathode electric discharge devices of all types may be utilized in the system shown in 4, in practice I prefer tubes having the properties of the Westinghouse KU-627 or KU-628 grid-glow tubes.

In the system shown in Fig. 5, the necessary variation in the grid or control potential is provided by phase shift circuits rather than by magnitude variation circuits. In. this view the electric discharge devices I51 and I59 that are illustrated as supplying the load are shown in a symbolical form representative of any device that might be utilized. In this system, as in the systerns shown in the other views, various types of electric discharge devices might be utilized, depending on the particular purpose for which the system is provided. Among the available electric discharge devices are gas-filled devices of the type having hot cathodes or vaporizable reconstructing cathodes (such as cathodes of mercury, tin, or of alkali metals), gas-filled devices having cathodes of the non-reconstructing type, and high vacuum devices of all types.

In the system shown in Fig. 5 the electric dis-- charge devices I51 and I59 are connected to the secondary section 9 of the transformer and to the load 3| in the same manner as the electric discharge devices 2| and 23 are connected in the system shown in Fig. 1. The anodes I6! and I53 of the electric discharge devices I5! and I59 are connected to the terminals II and I3 of the secondary section 9, while the cathodes I65 and I6! are connected to each other and their junction point 29 is connected to the center tap I5 of the section 9 through the load 3!.

The control electrodes I 59 and III of the devices I51 and I59 are not supplied with potential through contactor elements such as the elements of the system shown in Fig. 1 but are coupled to a plurality of similar phase-shift circuits or networks I13 and I15.

Each of the phase shift circuits I13 and I15 comprises a transformer secondary section I11 and E 19 provided with an intermediate tap I8I and I83 which is connected to a control electrode I59 and Ill of the respective electric discharge devices !51 and I59, through a suitable grid resistor I85 and I81. A network comprising an inductor I99 and I9I and a resistor I93 and I connected in series with the inductor, is connected to the terminal taps of each section I11 and I19 of the secondary 1. The junction point I91 and I99 of each of the sets of resistor I 93 and I95 and inductor I89 and I9I is connected to the terminals of a resistor 20I which has an intermediate tap 203 connected to the common junction point 29 of the cathodes I55 and I61.

The resistor 20! last-mentioned is capable of being alternately connected to and disconnected from an additional section 205 of the secondary 1 of the transformer 5, through a commutator 201' provided with an insulating segment 209 and a conducting segment 2! l, the commutator being rotated by the synchronous motor 31. When the resistor 295 is connected to the transformer section 295, it is connected directly across the section.

When the resistor 20I is disconnected from the secondary section 205, the potential supplied between each control electrode I69 or Ill and its associated cathode I55 or IE1 is determined solely by the phase shift circuits I13 or I15, respectively, and by the relationship of the magnitudes of the resistors I93 and I95 and the inductors I89 and I9! of the circuits. However, when the resistor ROI and the transformer section 205 are connected to each other, the control potential of the electric discharge device is varied by the application of the potential output of the section 205. Figs. 6 and 7 illustrate, vectorially and graphically, respectively, the condition of the electric discharge devices I51 and !59 when the resistor 29I is disconnected from the secondary section 295.

In Fig. 6, the principal potentials impressed on the electric discharge devices I51 and I59 are represented by horizontal vectors 2I3 and 2I5. The potentials impressed between the control electrode and the cathode of the electric discharge devices when the section 205 is disconnected from the system, are substantially the potentials impressed between the opposite points I8I, I91 and I83, I99 of the phase shift networks I13 and I15, and are represented by oblique vectors 2I1 and 2I9. The vectors 2H and 2I9 lag in phase behind the corresponding horizontal vectors 2I3 and 2I5 by considerable angles predetermined by the relationship of the impedances in each of the circuits I13 and I15. The phases of the principal potentials 2I3 and 2I5 applied to the two electric discharge devices I51 and I59 are maintained exactly opposite to each other, and hence the control-potential vectors 2I1 and 2I9 are necessarily colinear, being equal and opposite since the networks I13 and I15 are alike. The actual condition which results in either of the electric discharge devices when the vectorial relationship is as shown in Fig. 6 is illustrated in Fig. '1.

In Fig. 7 the principal potential supplied to the two electric discharge devices I51 and I59 is represented as a sine curve 22I, plotted against time. The portion of the curve above the axes of abscissa: may be regarded as the positive principal potential applied to one device I51, say, while the portion of the curve below the axes of abscissa: may be regarded as the corresponding positive principal potential applied to the other 5 electric discharge device I59. The limiting control-potential curve corresponding to the positive principal potential impressed on one electric discharge device I51 is shown as a broken-line curve 223 intersecting the positive principal-potential 10 half-ways. While the limiting control-potential curve is shown only for one of the electric discharge devices, it is apparent that a similar curve may be drawn for the other electric discharge device I59. The control potential is represented 15 as a sine curve 225 shifted in phase with respect to the principal-potential curve by a considerable angle. The control-potential curve 225 intersects the limiting control-potential curve 223 near the ends of the positive half-waves of the princi- 20 pal-potential curve 22I applicable to the corresponding electric discharge device I51. It is to be noted that if the potentials applied to the electric discharge devices I51 and I59 correspond in relationship to the curves shown in Fig. '1, each 5 of the electric discharge devices will be energized nearly at the end of each of a succession of positive half cycles of principal potential.

When the secondary section 205 is connected across the resistor 20I, an additional in-phase 30 potential is superimposed on each of the potentials provided by the phase-shifting circuits I13 and I15. This situation is represented vectorially in Fig. 8 and graphically in Fig. 9.

In Fig. 8 the principal potentials applied to the 35 electric discharge devices are represented by the opposite colinear vectors 2I3 and 2I5. The potentials applied to the control electrodes when the secondary section of the transformer is not connected in the system are represented by a 40 plurality of broken-line vectors 2I1 and 2I9 parallel to the corresponding vectors of Fig. 6. The potentials superimposed by the secondary section 205 are represented by a plurality of broken-line vectors 221 and 229 parallel to, and in the direc- 5 tion of the corresponding principal-potential vectors 2I3 and 2I5. The total potentials impressed on the control circuits of the respective electric discharge devices I51 and I59 are, therefore, represented by the sums of the two sets of 50 vectors 2I1 and 221 and 2I9 and 229 and, therefore, by the vectors 23I and 233 which lag in phase behind the principal-potential vectors 2I3 and 2I5, respectively, by an angle that is considerably smaller than the phase angles of the vec- 55 tors 2I1 and 2I9.

In the corresponding graphic diagram shown in Fig. 9, the control-potential curve is now shown at 235, intersecting the limiting control-potential curve 223 at points near the beginnings of 50 the positive half-waves of the principal-potential curve 22I, and the current transmitted through the electric discharge devices I51 and I59 from the power source is correspondingly of considerable magnitude. 05

As the commutator 201 is rotated, the control system varies from a condition corresponding to Fig. 8 and Fig. 9 to a condition corresponding to Fig. 6 and Fig. '1, and current is alternately supplied to the load 3| and drawn from the load 70 in a manner corresponding to that discussed hereinabove in connection with the systems shown in Figs. 1, 3, and 4. It is to be noted that if the curves shown in Fig. 9 and Fig. '1 are placed end to end, the resulting curve will correspond 75 to the curve shown in Fig. 2. As long as the system is in the condition represented in Fig. 9, power is supplied to the load 3| through the electric discharge devices I51 and I59. However, when the system is reverted to a condition such as is shown in Fig. '1, any power that is stored in the inductance of the load 3| is drawn therefrom and fed back into the power source through the electric discharge devices I51 and I59.

In the system shown in Fig. 10, the object of my invention is accomplished without the use of movable commutators or contactors. In this system the variation in control potential is attained by utilizing a timing circuit 236 of the type that is described in detail in a copending application Serial No. 650,517 filed January 6, 1933 by William W. Viebahn and assigned to the Westinghouse Electric & Manufacturing Company.

In the system shown in Fig. 10, the electric discharge devices I51 and I59 through which the load 3I is energized, are connected to the load and to a secondary section 9 of the transformer 5 in the same manner as the corresponding devices of the systems shown in Figs. 1, 3, 4, and 5. That is to say, the anodes I6I and I63 of the electric discharge devices are connected to the terminals II and I3 of the secondary section 9 while the cathodes I65 and I61 are connected together and their junction point 29 is connected to the intermediate tap I5 of the secondary section through the load 3|. Potential is supplied between the control electrodes I69 and HI and the associated cathodes I65 and I61 principally by a phase-shifting circuit 231 of the type incorporated in the system shown in Fig. 5. One output terminal 239 of the phase-shift circuit 231 is connected to the control electrode I69 of one of the electric discharge devices I51 through the usual grid resistor I and the other output terminal 24I of the circuit is connected to the control electrode III of the other electric discharge device I59, through the resistor I81.

A resistor 243 of suitable magnitude is connected between the control electrodes I69 and HI of the electric discharge devices I51 and I59. The varying potential is intermittently supplied from the timing circuit 236, the output leads 245 of which are connected between the junction point 29 of the cathodes I65 and I61 of the electric discharge devices I51 and I59 and an intermediate tap 241 of the resistor 243 connected between the control electrodes.

The timing circuit 236 comprises a plurality of electric discharge devices 249 and 25I which may be of the type utilized in the other portion of the system or may be hot-cathode gas-filled electric discharge devices, hot-cathode highvacuum electric discharge devices, or any other suitable devices. However, it is to be noted that preferably the electric discharge devices 249 and 25I should be of the gas-filled type and should have an abrupt characteristic similar to the characteristic of the other electric discharge devices utilized in the system.

The anodes 253 and 255 of the electric discharge devices 249 and 25I are connected to the terminal taps 251 and 259 of a secondary 26I of a transformer 263, the primary 265 of which is supplied with power from the bus lines I. The cathodes 261 and 269 of the devices are connected to each other and their junction point 21I is connected to the intermediate tap 213 of the secondary 26I through a potentiometer 215. The output leads 245 of the timing circuit 236 are connected to a movable tap 211 of the potentiometer 215 and to the central tap 213 of the secondary 26I. When either of the electric discharge devices 249 or 25I in the timing circuit 236 is energized, current is transmitted through the potentiometer 215 and a potential is impressed between the control electrodes I69 and III and the cathodes I65 and I61 of the electric discharge devices I51 and I59.

The common junction point 21 I of the cathodes 261 and 269 of the electric discharge devices 249 and 25I in the timing circuit 236 is connected to the lower or positive plates 219 and 28I of a plurality of biasing-potential capacitors 283 and 285 while an additional intermediate tap 281 of the potentiometer 215 is connected to the upper or negative plates 289 and 29I of the capacitors through a plurality of resistors 293 and 295. One oi these resistors 293 is connected between one capacitor 283 and the movable tap 281 while the other of the resistors 295 is connected between the two capacitors 283 and 285. The junction point 291 of the capacitor 285 and the latter resistor 295 is connected to the movable tap 299 of a unidirectionally energized biasing potentiometer 30I, the positive terminal 303 of which is in turn connected to the intermediate tap 305 of the secondary 301 of an additional transformer 909 that is energized from the bus lines I. The terminal taps 3H and 3I3 of the secondary 301 are connected to the control electrodes 3I5 and 3I1 of the electric discharge devices 249 and 25I.

The timing feature of the circuit 236 is dependent on the relationship between the biasingpotential capacitors 283 and 285 and the resistors 293 and 295. The operation of the system is described in detail in the above-mentioned Viebahn application. However, it may be explained shortly here.

Assume for the purpose of the present explanation that the biasing-potential capacitors 283 and 285 are substantially in uncharged condition. The control potential supplied to the electric discharge devices 249 and 25I by the biasing potentiometer 30I and the transformer-secondary 301 is not sufficiently negative to block the energization of either one of the electric discharge devices. Assume then that the principal potential on the right-hand electric discharge device 25I is positive. In such a case the right-hand electric discharge device is energized and current is transmitted through the potentiometer 215. By reason of the current thus transmitted, a difference of potential is impressed between the output leads 265 of the timing system. When the principal.

potential changes in polarity and the left-hand electric discharge device 249 has positive principal potential impressed thereon it is energized and the supply of current to the potentiometer continues.

As the timing-circuit electric discharge devices 249 and 25I are energized, a potential difference exists between the common cathode terminal 21I and the movable tap 281 of the potentiometer 215. The biasing-potential capacitors 283 and 285 are, therefore, charged, the lower plates 219 and 28I accumulating a positive charge while the upper plates 289 and 29I accumulate a negative charge.

The left-hand capacitor 283 is moreover charged to a greater potential than the righthand capacitor 285 since the resistance in series with the former is less than the resistance in series with the latter.

As the electric discharge devices 249 and 25I continue to supply current to the potentiometer 215, a negative potential is superimposed on the biasing potential and the alternating potential that are impressed between the control electrodes M5 and 3!? and the cathodes 261 and 269 of the timer-circuit electric discharge devices 249 and 253, through the biasing potentiometer 3M and the secondary 331 of the transformer 399, respectively. When the negative potential attains a proper value, the electric discharge devices 249 and 25I are deenergized and the supply of current to the potentiometer 215 ceases. The capacitors and 285 are then discharged through the resistors 293 and 295 and the potentiometer 215. The control potentials impressed on the electric discharge devices 249 and 25! eventually attain such values that the electric discharge devices are again energized. This series of operations is repeated continuously as long as power is applied to the system.

Although certain of the elements such as the biasing potential and the alternating potential supplied to the control circuits of the timing electric discharge system .c not concern the present invention and are enplained in detail in the above-mentioned Viebahn application, a word might be said about them here.

Two biasing-potential capacitors 283 and 285 are utilized instead of one, in order to extend the periods during which th electric discharge devices 2 39 and 25I are deenergized and energized. It is to be n ted that the right-hand capacitor 235, which is connected to the control electrodes 3I5 and 3H, determines when the control electrodes will attain negative potentials of such magnitude as to interrupt the discharging condition of the electric discharge devices. The lefthand capacitor however, is maintained at a higher potential dilie'rence than the right-hand capacitor 235 and maintains the latter in charged condition for an interval after the charging potential has been removed. Consequently, when the electric discharge devices are deenergized, the right-hand capacitor 285 is not at once discharged to produce a re-energized condition in the electric discharge devices. 249 and 25I but remains in charged condition for an interval dependent on the magnitudes of the other elements in the system.

The biasing potential of the potentiometer 30I is provided in the timing system for the purpose of extending its range. The alternating potential applied by the secondary 331 of the transformer 309 is in opposite phase to the alternating principal potential supplied to the electric discharge devices 243 and and is provided for the purpose of increasing the sharpness of the variation in the conditions of the timing system 236.

The operation of the system is illustrated in the vectorial diagram of Fig. 11 and the graph of Fig. 12. When the electric discharge devices 243 and 25! of the timing circuit 236 are deenergized the junction point 29 and the intermediate tap 2 are substantially at the same potential and the phase-shift circuit 231 determines the potential relationship of the electric discharge devices 151 and I58 in the power supply system and the principal potential is related to the control potential in accordance with the vector diagram of Fig. 11.

In Fig. ll, the principal potentials on the two electric discharge devices are represented as opposite colinear horizontal vectors 3I9 and 32I, while the control potentials are represented by oblique vectors and 325 that are also colinear. The latter vectors 323 and 325 lag in phase behind the principal potential vectors 3I9 and MI by alarge angle.

In Fig. 12 the principal potential which is supplied to the two electric discharge devices I51 and I59 is represented by a full-line sine wave 5 321. The control potential when the timing circuit 236 is deenergized is represented by a brokenline curve 329 which is a substantial angle out of phase with the principal potential curve. To simplify matters, it may be assumed that the 1 limiting control potential curve of the two main electric discharge devices I51 and I59 is the axis of abscissa: 33I.

It will be noted that, in the case represented by the curves 321 and 329, when the timing circuit 236 is deenergized, the electric discharge devices I51 and I59 become energized near the ends of the positive half-cycles of principal potential supplied thereto. l-a'oreover, in the system shown in Fig. 10, the control electrodes I69 and IH of the electric discharge devices I51 and I59 are connected to opposite terminals 239 and MI of the phase-shift circuit 231. Consequently, the two electrodes are always in opposite phase to each other, and the control potentials 323 and 325 applied to the respective electric discharge devices I51 and I59 are related to the respective principal potentials 3 I9 and 32I as shown in Fig. 11. When the timing circuit is deenergized, therefore, the electric discharge devices I51 and I50 are energized substantially at the ends of each of a series of successive half-cycles.

When the electric discharge devices 249 and 25I of the timing circuit are energized. half-wave pulses of current are transmitted through the potentiometer 215 and the corresponding potentials are impressed between the intermediate tap 241 of the resistor 243 connected to the control electrodes :69 and HI of the electric discharge devices I51 and I59 and the junction point 0 29 of their cathodes I65 and I61. These halfwaves are substantially in phase with the corre sponding half-waves of the principal potential applied to the electric discharge devices I51 and I59 and may be represented by a series of half- 5 wave curves 333, as in Fig. 12. The not control potential impressed on the electric discharge devices I51 and I59 through which the load 3I is energized may be represented by a curve 335 equal to the sum of the control potential 329 supplied by the phase-shift circuit 231 and the potential 333 sup-plied by the timing circuit 236. It is to be noted that this control-potential curve 335 either intersects the axis 33I of abscissa: very near to the beginnings of the half-waves of prin- 55 cipal potential or lies above the axis 33I nearly up to the various points at which the principal potential changes. Accordingly, when the timing circuit 236 is energized, the electric discharge devices i51 and I 59 whereby power is supplied to the 60 load 3| are both at first, energized substantially at the beginnings of the positive half-cycles of principal potential supplied to them.

Since the condition of the timing circuit 236 varies intermittently, the electric discharge devices whereby the load 3| is energized will be intermittently energized for a number of positive half cycles at or near the beginning of each of the half cycles and then for a second suc- I cession of half cycles at or near the end of each half cycle. The power source will, therefore, supply energy to the load during the first set of intervals when the timing circuit is energized and will draw energy from the load during the second set of intervals when the timing circuit is deenergized.

I have shown and described in the present application a number of different modifications. My invention is, therefore, not to be restricted to any particular modification, nor is it to be restricted to a system in which a particular type of electric discharge device is utilized. It is to be noted first that while independent electric discharge devices have been illustrated herein as supplying half pulses of current to the load and as drawing half wave pulses of current from the load, such independent devices need not necessarily be utilized. Electric discharge devices in which a common cathode and a plurality of anodes are incorporated are well known in the art and such devices may be utilized in lieu of the devices shown herein. The same principal applies to electric discharge devices having a plurality of cathodes and a common anode.

Moreover, it should be noted that the timing circuit of the system shown in Fig. in lieu of being applied with electric discharge devices of the control electrode type may be applied to a system of the type shown in Fig. 3 or Fig. 5, in which make-alive electric discharge devices are incorporated. In this system the timing circuit will, of course, replace the rotary switch system.

Again, it is well to note that the phase shift system of the type shown in Fig. 5 may replace either of the systems shown in the other views. In all cases where the make alive electric discharge devices are utilized instead of the control electrode electric discharge devices, the operation of the system depends on a current supply to the electric discharge devices rather than on potential variations. However, the current in the absence of phase shifting impedances varies in accordance with the potential and no difiiculties are involved in replacing one type of electric discharge device by another.

Finally, attention is called to the fact that my invention should not be restricted to apply only in the limited scope of an improvement of the system shown in my earlier application. Essentially, my invention is directed to a system for converting power of one frequency into power of another frequency. If instead of the pulsating current that is obtained in the systems described hereinabove, alternating current of the lower frequency is desired, a simple system for attaining this purpose may be provided in accordance with my invention.

In such apparatus, two similar systems of the type described hereinabove are provided. The loads 3| of the two systems are the primaries of a common transformer having a single secondary and the systems are so connected that the supply of pulses to one load or primary is of opposite polarity to the supply of pulses to the other load or primary.v The contactors 33 and 35 or H5 and III or the timing circuits 236 of the systems whereby the loads are supplied are of such character that after a pulse is supplied to one primary no further current is supplied to it for the period of time during which the pulse is supplied and during this interval a pulse is supplied to the other primary that is of opposite polarity to the pulse supplied to the first primary. Accordingly, in the secondary of the transformer, a current will be induced by the periodicity of the pulses.

It is to be noted that more than two systems such as are described hereinabove may also be utilized to feed the primaries of a common transformer. In such a case, the currents supplied to the individual primaries bear a predetermined phase relationship to each other and plural phase power is supplied by the secondary of the transformer. 5

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the 10 prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination in a power supply system for a load of the type having the property of storing a portion of the energy supplied thereto, an alternating power supply source, a set of electrodes between which an electric discharge is to be transmitted, another set of electrodes between which an electric discharge is to pass, each of said sets of electrodes being of such character that the discharge of only one polarity can be transmitted therebetween, means for so coupling said sets of electrodes to said power source and to said load that when the potential impressed across one of said sets of electrodes is of such polarity that said set is conductive to the discharge current transmitted under the electromotive force of said potential the other set of electrodes is non-conductive to the discharge current that would be transmitted under the elec- 80 trornotive force thereof and when the potential is of such polarity that said last-named set is conductive to the discharge current transmitted under the electromotive force thereof said first named set is non-conductive, means, associated 85 with each of said of electrodes, for initiating a discharge thereb-etween when the potential impressed between said electrodes is of proper polarity for the transmission of a discharge, means for actuating said discharge initiating means to initiate a discharge between each of the electrodes of said sets substantially at the beginnings of a group of successive intervals during which the potentials impressed between the electrodes of said sets by said power source is of proper polarity for the transmission of a discharge between said sets, whereby current is transmitted from said source to said load through said sets of electrodes, and means for activating said discharge initiating means to initiate a discharge between each of the electrodes of said sets substantially at the ends of a group of successive intervals during which the potentials impressed between the electrodes of said sets is of proper polarity for the transmission of a discharge therebetween, whereby energy stored in said load is fed back into said pewer source through said sets of electrodes.

2. In combination a power supply system for a load of the type having the property of storing a portion of the energy supplied thereto, an alternating power supply source, a set of electrodes between which an electric discharge is to be transmitted, another set of electrodes between which an electric discharge is to be transmitted, each of said sets of electrodes being of such character that the discharge only one polarity can be transmitted therebetween, means for so coupling said sets of electrodes to said power source and to said load that when the potential impressed across one of said sets of electrodes by said power source is of such polarity that said set is conductive to the discharge current transmitted under the electromotive force of said potential the other set of electrodes is non-conductive to the discharge current that would be transmitted under the electromotive force thereof and when the potential is of such polarity that said last-named set is conductive to the discharge current transmitted under the electromotive force thereof, said first-named set is non-conductive, means, associated with each of said sets of electrodes, for initiatin a discharge therebetween, each of said sets of electrodes remaining nonconducting, even when the potential impressed between said electrodes is of proper polarity for the transmission of a discharge, when its associated initiating means is in a non-activated condition, and means for activating said initiating means associated with each of said sets substantially at the beginnings of each of a group of successive half cycles during which the potential of said source is such that each set is in its turn conductive to discharge current transmitted under the electromotive force of said potential whereby current is transmitted from said source to said lead through said sets of electrodes and for activating said initiating means near the ends of each of another group of half-cycles during which the potential impressed between the electrodes of each set in its turn is such that said sets are conductive to the discharge current therebetween, said first-named group of halfcycles being separated from said last-named group of half-cycles by nearly a half-cycle during which said initiating means is unactivated, whereby the energy stored in said load is fed through said sets of electrodes into said source.

3. Apparatus for supplying power to a load of the type that has the property of storing a portion of the energy supplied thereto, comprising means, including a transformer winding having a plurality of terminal taps and an intermediate tap, for supplying alternating power, a plurality of pairs of electrodes between which an electric discharge current is to be transmitted, means for coupling an electrode of one of said pairs to one terminal tap of said winding, means for coupling the corresponding electrode of another of said pairs to another terminal tap of said winding, means for coupling the other electrodes of said pairs to each other, means for coupling said lead between the electrical junction point of said last-named electrodes and the intermediate tap of said winding, means, associated with each of said pairs of electrodes, for initiating a discharge between said electrodes when the principal potential impressed therebetween from said power source is positive, and means for activating said initiating means to respectively initiate the discharge between said pairs of electrodes substantially at the beginnings of each half cycle of a group of successive positive half cycles of principal potential, whereby said load is supplied with energy from said source through said pairs of electrodes, and for activating said initiating means to initiate the discharge between said pairs of electrodes near the ends of each halfcycle of a group of successive positive half cycles of principal potential, separated from said first named group of half-cycles by nearly a complete half-cycle of principal potential, whereby the energy stored in said lead is fed back into said source through said sets of electrodes.

4. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plu rality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of electrodes to impress potentials between the electrodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed across the electrodes of one set is in opposite phase to the potential impressed across the electrodes of another set, means, associated with each of said sets of electrodes to be activated, for initiating an electric discharge between the electrodes of its associated set, and means for activating said initiating means, to initiate the discharge alternately between the electrodes of each of said sets substantially at the beginnings of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each set in its turn, that is of such polarity that the particular set of electrodes is conductive to the discharge current transmitted under the electromotive force of said potential, whereby said load is energized from said power supply through said sets of electrodes, and for subsequently activating said initiating means near the ends of each half cycle of a plurality of successive half cycles of potential, impressed between the electrodes of each of said sets in its turn, that is of such plarity that the particular set is conductive to discharge current transmitted under the electromotive force thereof, whereby the energy stored in said load is fed back into said power source through said sets of electrodes.

5. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plurality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of electrodes to impress potentials between the electrodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed across the electrodes of one set is in opposite phase to the potential impressed across the electrodes of another set, means, associated with each of said sets of electrodes for initiating an electric discharge therebetween, said initiating means being adapted to be activated by means of a potential of a predetermined magnitude and polarity relative to the magnitude and polarity of the potential impressed between the electrodes of its associated set, and means for impressing activating potentials of proper magnitude and polarity to said initiating means of each of said sets to activate said initiating means, and to initiate the discharge alternately between the electrodes of each of said sets substantially at the beginnings of each half cycle of a plurality of successive half-cycles of potential, impressed between the electrodes of each set in its turn, that is of such polarity that the particular set of electrodes is conductive to the discharge current transmitted under the electromotive force of said potential, whereby said load is energized from said power supply through said sets of electrodes; and for subsequently impressing activating potentials of proper magnitude and polarity to said initiating means of each of said sets to activate said initiating means near the ends of each half cycle of a plurality of successive half cycles of potential, impressed between the electrodes of each of of said sets in its turn, that is of such polarity that the particular set is conductive to discharge current transmitted under the electromotive force thereof, whereby the energy stored in said load is fed back into said power source through said sets of electrodes.

6. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plurality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of electrodes to impress potentials between the electrodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed across the electrodes of one set is in opposite phase to the potential impressed across the electrodes of another set, means associated with each of said sets of electrodes for intiating an electric discharge therebetween, said initiating means being adapted to be activated by means of a potential of a predetermined magnitude and polarity relative to the magnitude and polarity of the potentials impressed between the electrodes of its associated set, means for impressing, on the initiating means associated with each of said sets of electrodes, alternating potentials that are of such magnitudes, phases and polarities relative to the potentials impressed between the corresponding electrodes of the sets that said initiating means is activated to initiate a discharge between the electrodes of said sets in their turn substantially at the beginnings of a plurality of half cycles of potential, impressedv between the electrodes of said sets, that are of such polarity that said sets are conductive to the discharge current transmitted under the electromotive forces thereof, whereby said load is energized from said source through said sets of electrodes; and means for subsequently shifting the phase of said alternating potential impressed on each of said initiating means to such a point that said initiating means are activated to initiate the discharge near the ends of a plurality of successive half cycles of potential, impressed on the electrodes of each of said sets in its turn, that are of such polarity that the sets of electrodes are conductive to a discharge current transmitted under the electromotive force thereof, whereby the energy stored in said load is fed back into said source thorugh said sets of elec trodes.

7. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plurality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of electrodes to impress potentials between the electrodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed across the electrodes of one set is in opposite phase to the potential impressed across the electrodes of another set, means associated with each of said sets of electrodes for initiating an electric discharge therebetween, said initiating means being 5 adapted to be activated by the passage of a current of a predetermined magnitude and polarity, relative to the magnitude and polarity of the potential impressed between the electrodes of its associated set, transmitted through it and through an electrode of the corresponding set, and means for transmitting current of proper polarity and magnitude through each of said initiating means and the cooperating electrode of its associated set, to initiate the discharge al- 16 ternately between the electrodes of each of said sets substantially at the beginnings of each half cycle of a plurality of successive half cycles of potential, impressed between the electrodes of each set in its turn, that is of such polarity that 20 the particular set of electrodes is conductive to the discharge current transmitted under the electromotive force of said potential, whereby said load is energized from said power supply through said sets of electrodes, and for transmitting currents of proper polarity and magnitude between each of said initiating means and the cooperating electrode of its associated set near the ends of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each of said sets in its turn, that is of such polarity that the particular set is conductive to discharge current transmitted under the electromotive force thereof, whereby the energy stored in said load is fed back into said power source through said sets of electrodes.

8. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plurality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of electrodes to impress potentials between the electrodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed across the electrodes of one set is in opposite phase to the potential impressed across the, electrodes of another set, means associated with each of said sets of electrodes for initiating an electric discharge therebetween, said initiating means being adapted to be activated by the passage of a current of a predetermined magnitude and polarity, relative to the magnitude and polarity of the potential impressed between the electrodes of its associated set, transmitted through it and through an electrode of the corresponding set, means for transmitting through each of the initiating means and the cooperating electrodes of its associate set, alternating currents that are of such magnitude, phases and polarities relative to the potentials impressed between the electrodes of each of said sets that said initiating means is activated to initiate a discharge between the electrodes of said sets in their turn substantially at the beginnings of a plurality of half cycles of potential, impressed between the electrodes of said sets, that are of such polarity that said sets are conductive to the discharge current transmitted under the electromotive force thereof, whereby said load is energized from said source through said sets of electrodes, and means i or subsequently shifting the phase of said alternating current transmitted through said initiating means to such a point that said initiating means is activated to initiate the discharge near the ends or a plurality of successive half cycles of potential, impressed by said power source on the electrodes of each of said sets in its turn, that are of such polarity that the sets of electrodes are conductive to a discharge current transmitted under the electro-motive force thereof, whereby the energy stored in said load is fed back into said source through said sets of electrodes.

9. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plurality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of electrodes to impress potentials between the electrodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed across the electrodes of one set is in opposite phase to the potential impressed across the electrodes of another set, means associated with each of said sets of electrodes for initiating an electric discharge therebetween, said initiating means being adapted to be activated by the passage of a current of a predetermined magnitude and polarity, relative to the magnitude and polarity of the potential impressed between the electrodes of its associated set, transmitted through it and through an electrode of the corresponding set, and means including a plurality of electric discharge devices associated with said in- 'itiating means, a separate one of said electric discharge devices being associated with the initiating means that cooperates with each set of electrodes, for transmitting currents of proper polarity and magnitude through each of said initiating means and the cooperating electrode of its associated set to initiate the discharge alternately between the electrodes of each of said sets substantially at the beginnings of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each set in its turn, that is of such polarity that the particular set of electrodes is conductive to the discharge current transmitted under the electromotive force of said potential, whereby said load is energized from said power supply through said sets of electrodes, and for transmitting currents of proper polarity and magnitude through each of said initiating means and the cooperating electrode of its associated set near the ends of each half cycle of a plurality of successive half cycles of potential, impressed between the electrodes of each of said sets in its turn, that is of such polarity that the particular set is conductive to discharge current transmitted under the electromotive force thereof, whereby the energy stored in said load is fed back into said power source through said sets of electrodes.

10. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plurality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of elec trodes to impress potentials between the elec trodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed between the electrodes of one set is in opposite phase to the potential impressed between the electrodes of another set, means, associated with each of said sets of electrodes to be activated, for initiating an electric discharge between the electrodes of its associated set, means for activating said initiating means, to initiate the discharge alternately between the electrodes of each of said sets substantially at the beginnings of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each set in its turn, that is of such polarity that the particular set of electrodes is conductive to the discharge current transmitted under the electromotive force of said potential, whereby said load is energized from said power supply through said sets of electrodes, and means for subsequently varying the activation of said initiating means in such manner that the discharge is initiated near the ends of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each of said sets in its turn, that is of such polarity that the particular set is conductive to discharge current transmitted under the electromotive force thereof, whereby the energy stored in said load is fed back into said power source through said sets of electrodes.

11. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plurality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of elec trodes to impress potentials between the electrodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed between the electrodes of one set is in opposite phase to the potential impressed between the electrodes of another set, means, associated with each of said sets of electrodes to be activated, for initiating an electric discharge between the electrodes of its associated set, means for activating said initiating means, to initiate the discharge alternately between the electrodes of each of said sets substantially at the beginnings of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each set in its turn, that is of such polarity that the particular set of electrodes is conductive to the discharge current transmitted under the electromotive force of said potential, whereby said load is energized from said power supply through said sets of electrodes; and means, including an electrical timing circuit, for subsequentlyvarying the activation of said initiating means in such manner that the discharge is nitiated near the ends of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each of said sets in its turn, that is of such polarity that the particular set is conductive to discharge current transmitted under the electromotive force thereof, whereby the energy stored in said load is fed back into said power source through said sets of electrodes.

12. Apparatus for supplying power to a load of the type having the property of storing a portion of the energy supplied thereto, comprising a plurality of sets of electrodes between which an electric discharge current is to pass, the electrodes of each of said sets being of such character that each set passes discharge current of one polarity and prevents the passage of discharge current of the opposite polarity, power supply means cooperating with said sets of electrodes to impress potentials between the electrodes of each of said sets, the cooperative relationship of said power supply means and said sets of electrodes being such that the potential impressed across the electrodes of one set is in opposite phase to the potential impressed across the electrodes of another set, means, associated with each of said sets of electrodes to be activated, for initiating an electric discharge between the electrodes of its associated set, means for activating said initiating means to initiate the discharge alternately between the electrodes of each of said sets substantially at the beginnings of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each set in its turn, that is of such polarity that the particular set of electrodes is conductive to the discharge current transmitted under the electromotive force of said potential, whereby said load is energized from said power through said sets of electrodes, and means, including an electrical timing circuit of the type incorporating an electric discharge device, for subsequently varying the activation of said initiating means in such manner that the discharge is initiated near the ends of each half cycle of a plurality of successive half cycles of potential impressed between the electrodes of each of said sets in its turn, that is of such polarity that the particular set is conductive to discharge current transmitted under the electromotive force thereof, whereby the energy stored in said load is fed back into said power source through said sets of electrodes.

13. The method of utilizing an asymmetrically conducting device to supply power intermittently from an alternating power supply source to a load of the type having the property of storing a portion of the energy supplied thereto; which comprises intermittently supplying energy to said load through said device during a plurality of intervals during which the polarityof the potential of said power source is such that said device is conductive thereto, for a predetermined period of time, and subsequently, for a second predetermined period of time, intermittently feeding the resultant energy stored in said load back into said power source through said device during a plurality of intervals during which the polarity of the potential of said power source is such that said device is non-conductive thereto, and simultaneously, during the second-mentioned period of time, intermittently providing an alternative electrical path interconnecting said source and said load, in such manner as to exclude said device during substantially all of the intervals during which the principal potential supplied thereto from said source is of such polarity that said device is conductive thereto, thereby preventing any considerable amount of energy from being supplied to said load while the load is feeding energy back to said source.

14. Power-supply apparatus for a load of the type having the property of storing a portion of the energy supplied thereto, comprising a powersupply source, an electric discharge device incorporating means to be energized for initiating a discharge therein, means for coupling said electric discharge device between said load and said source, means for energizing said initiating means in such manner as to cause said discharge device to transmit power from said source to said load for a predetermined period of time, means for thereafter changing the condition of said discharge-initiating means in such manner as to cause said discharge device to transmit power from said load to said source for a second period of time, whereby, during the latter period of time, the energy stored in said load is fed back to said source through said discharge device, and means for preventing the supply of any considerable amount of power from said source to said load during said second period of time.

15. The method of utilizing a plurality of asymmetrically conducting electric discharge devices to supply power from an alternating powersupply source to a load of a type having the property of storing a portion of the energy supplied thereto; which comprises so energizing said electric discharge devices that when the polarity of the potential of said source as applied to one of said devices is such that said device is conductive to current transmitted under the electromotive force thereof, the polarity of said source as applied to another of said devices is such that the latter device is non-conductive to current transmitted under the electromotive force thereof, and vice versa, alternately energizing said first-named electric discharge device and said last-named electric discharge device for a predetermined period of time in successive intervals during which the polarity of the potential of said power source is such that each of said devices is respectively conductive to the current transmitted under the electromotive force thereof, to supply current to said load, and, for another period of time, immediately succeeding the firstmentioned period, causing said discharge devices to be respectively deenergized substantially during the intervals during which the potentials im pressed thereon from said source are of such polarity that said discharge devices would be conductive to the current transmitted under the electromotive force thereof, while causing said discharge devices to be energized substantially during the intervals during which the potentials supplied by said source are of the opposite polarities, whereby the energy stored in said lead is fed back to said source.

16. The method of utilizing a plurality of asymmetrically conducting electric discharge devices to supply power from an alternating'powersupply source to a load of the type having the property of storing a portion of the energy supplied thereto, each of said devices having a control electrode and a piurality of principal electrodes, and being of type having an energized condition and a deenergized condition, and being capable of only abrupt transiti n from said deenergized condition to said energized condition when the potentials impressed between said prim cipal electrodes and between said control elec trode and one of its principal electrodes attain values related to each other in a let-erini d manner in magnitude and in polarity, being capable of transition from said energized condition to said deenergized condition only when the potential impressed between said principal electrodes attains a predetermined lower limit; said method comprising the steps of so coupling said electric discharge devices between said load and said power source that when th polarity of the potential of said power source is such that one of said discharge devices is conductive to current transmitted under the electroniotive force of said power source, another of said discharge devices is non-conductive thereto, and when the polarity of said source is such that said last-named device is conductive to said current said first-named device is non-conductive; impressing such potentials between said principal electrodes and between the control electrode of each device and its associated principal electrode that said devices are alternately in energized condition under the influence of the potential of the power source, for a predetermined period of time, while the potential of said source is such that each of said devices is respectively conductive to the current transmitted under the electromotive force thereof, thereby to transmit current to said load from said power source; and subsequently, for a second period of t me, :ressing such potentials between said pri cipal electrodes and between the control electrode of each device and its associated principal ectrode that said devices are in deenergized condition, while the potentials of said source are such that current can be transmitted through discharge device under the electromotive force thereof, but in energized condition under the influence of the potential arising by reason of the stored energy in load, while the potentials of said source are such that said discharge devices are non-conductive to current transmitted under the elec emotive force thereof, whereby the energy stored in said load is fed back into said power source.

1'7. Apparatus for supplying power intermittently from an alternating power supply source to a load of the type having the property of storing a portion of the energy supplied thereto, comprising, in combination, an asymmetrically conducting dcvice, means for intermittently supplying energy to said load through said device during a plurality of intervals during which the polarity of the potential of said power source is such that said device is conductive thereto, for a predetermined period of time, and means for subsequently, for a second predetermined period of time, intermittently feeding th resultant energy stored in said load back into said power source through said device during a plurality of intervals during which the polarity of the potential of said power source is such that said device is non-conductive thereto, said last-mentioned means includ g means for simultaneously, during the secoi d-mentioned period of time, intermittently providing an alternative electrical path interconnecting said source and said load, in such manner as to ex lude said device during substantially all of the rvals during which the principal potential supplied thereto from said source is of such polarity that device is conductive thereto, thereby preventing any considerable amount of energy from being supplied to said load while the load is feeding energy back to said source.

18. Apparatus for supplying power from an alternating power-supply source to a load of a type having the proper y of storing a portion of the energy supplied th reto, comprising, in combination, a plurality of asymmetrically conducting electric discharge devices, means for so energizing said electric discharge devices that when the polarity of the potential of said source as applied to one of said devices is such that said device is conductive to current transmitted under the electromotive force thereof, the polarity of said source as applied to another of said devices is such that the latter device is non-conductive to current transmitted under the electromotive force thereof, and vice versa, means for alternately energizing said first-named electric discharge device and said last-named electric discharge device for a, predetermined period of time in successive intervals during which the polarity of the potential of said power source is such that each of said devices is respectively conductive to the current transmitted under the electromotive force thereof, to supply current to said load, and, means operative for another period of time, immediately succeeding the first-mentioned period, for causing said discharge devices to be respectively deenergized substantially during the intervals during which the potentials impressed thereon from said source are of such polarity that said discharge devices would be conductive to the current transmitted under the electromotive force thereof, while causing said discharge devices to be energized substantially during the intervals during which the potentials supplied by said source are of the opposite polarities, whereby the energy stored in said load is fed back to said source.

19. Apparatus for supplying power from an alternating power-supply source to a load of the type having the property of storing a portion of the energy supplied thereto, comprising, in combination, a plurality of asymmetrically conducting electric discharge devices, each of said devices having a control electrode and a plurality of principal electrodes, and being of a type having an energized condition and a deenergized condition, and being capable of only abrupt transition from said deenergized condition to said energized condition when the potentials impressed between said principal electrodes and between said control electrode and one of its principal electrodes attain values related to each other in a. predetermined manner in magnitude and in polarity, and being capable of transition from said energized condition to said deenergized condition only when the potential impressed between said principal electrodes attains a predetermined lower limit, means for so coupling said electric discharge devices between sald load and said power source that when the polarity of the potential of said power source is such that one of said discharge devices is conductive to current transmitted under the electromotive force of said power source, another of said discharge devices is non-conductive thereto, and when the polarity of said source is such that said last-named device is conductive to said current said first-named device is nonconductive, means for impressing such potentials between said principal electrodes and between the control electrode of each device and its associated principal electrode that said devices are alternately in energized condition under the influence of the potential of the power source, for a predetermined period of time, while the potential of said source is such that each of said devices is respectively conductive to the current transmitted under the electromotive force thereof, thereby to transmit current to said load from said power source, and means for subsequently, for a second period of time, impressing such potentials between said principal electrodes and between the control electrode of each device and its associ- 7 

